linux-kernel - [patch] lib/scatterlist: error handling in __sg_alloc

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Message-ID: <20130620081218.GC15095@elgon.mountain>
Date:	Thu, 20 Jun 2013 11:12:18 +0300
From:	Dan Carpenter <dan.carpenter@...cle.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Imre Deak <imre.deak@...el.com>,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	Maxim Levitsky <maximlevitsky@...il.com>,
	Tejun Heo <tj@...nel.org>, linux-kernel@...r.kernel.org
Subject: [patch] lib/scatterlist: error handling in __sg_alloc_table()

I was reviewing code which I suspected might allocate a zero size SG
table.  That will cause memory corruption.  Also we can't return before
doing the memset or we could end up using uninitialized memory in the
cleanup path.

Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>

diff --git a/lib/scatterlist.c b/lib/scatterlist.c
index a1cf8ca..d39178b 100644
--- a/lib/scatterlist.c
+++ b/lib/scatterlist.c
@@ -247,13 +247,15 @@ int __sg_alloc_table(struct sg_table *table, unsigned int nents,
 	struct scatterlist *sg, *prv;
 	unsigned int left;
 
+	memset(table, 0, sizeof(*table));
+
+	if (nents == 0)
+		return -EINVAL;
 #ifndef ARCH_HAS_SG_CHAIN
 	if (WARN_ON_ONCE(nents > max_ents))
 		return -EINVAL;
 #endif
 
-	memset(table, 0, sizeof(*table));
-
 	left = nents;
 	prv = NULL;
 	do {
--
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